1. Field of the Invention
The present invention relates to pull cords for effecting and controlling the movement of loads such as covers, including but not limited to window covers. The present invention also relates to drive systems such as spring drives or motors, including flat (or spiral coil) and coil spring drives, which are useful in numerous applications for effecting and controlling the movement of loads, including but not limited to covers, including window covers, and to other components which are useful in combination with such spring drives.
2. Definitions and Applicability
Springs of the type shown for example in FIGS. 5C, 7C, 9C and 10C typically are referred to herein as coil springs. Springs of the type shown for example in FIGS. 6–8 typically are referred to herein as flat springs.
Typically, as used herein, the word “cover” refers to expandable or extendible structures such as blinds and drapes. These include slat structures such as so-called venetian or slat blinds and so-called mini-blinds. These structures also include pleated folding structures such as single and plural pleat structures and box, hollow and cellular structures. “Cover” also refers to flat, sheet-type covers such as roller blinds. In this document, “cover” and “blind” are frequently used interchangeably. As applied to such covers, “operate” refers to the process of closing and opening the covers, typically (for horizontally oriented or extending covers with the cover mounted and collected at the top) to lowering and raising the cover.
As used here, “horizontal” window cover refers to horizontally oriented covers such as horizontal slat blinds, horizontal folded-pleat blinds and drapes and horizontal cellular blinds and drapes. The present invention is applicable generally to horizontal window cover systems and to flat window cover systems. It is understood that “window,” as used for example in “window cover,” includes windows, doorways, openings in general and non-opening areas or regions to which covers are applied for decoration, display, etc.
As used here, the terms “operatively connected,” “operatively coupled,” “operatively connected or coupled” and the like include both direct connections of one component to another without intervening components and connections via intervening components including gears, transmissions, etc. Also, “plurality” means two or more.
3. Current State of the Relevant Technology
a. Pull Cords
Typically, when used to control loads such as a cover or window cover, single pull cords can be used to pull the associated load in a single direction. Endless cords are used to pull the load in opposite directions.
Accordingly, in is one object of the present invention to provide a single pull cord mechanism which has the ability to pull loads such as covers and window covers in opposite directions, for example, to both extend and retract the load.
b. Slat and Resilient ((Pleated) Blinds
Typically a horizontal cover or blind is mounted above the window or space which is to be covered, and is operated using lift cords to extend the cover and lower it across the area, stopping at a selected position at which the blind partially or fully covers the area. For typical horizontal slat blinds, the lift cords are attached to a bottom rail and the “rungs” or cross-members of a separate cord ladder are positioned beneath the slats of the blind. When the blind is fully lowered, each slat is supported by a rung of the blind's cord ladder and relatively little weight is supported by the lift cords. However, as the blind is raised, the slats are “collected” on the bottom rail, and the support of the slats is thus increasingly transferred from the cord ladder to the bottom rail and the weight supported by the rail and the associated lift cords increases.
Many pleated, cellular, box, etc., blinds are formed of resilient material having inherent spring-like characteristics. As the resilient pleated blind is raised toward the fully open position, the blind material is increasingly compressed, and requires increasingly greater force to overcome the compression force and move the blind and hold the blind in position. Conversely, as the blind is extended and lowered toward a closed position, the compression of the pleats decreases. Effectively, then, both the slat blind and the pleated blind require increasingly greater force to open or raise the blind and to maintain the blind open than is required to close or lower the blind and maintain the blind closed.
c. Flat and Coil Spring Drives
The operating characteristics of conventional coil spring drives and conventional constant torque flat spring drives are not ideally suited to assist the opening and closing operation of horizontal and flat blinds, especially long or heavy blinds. As applied to downward-closing embodiments of such blinds, such spring drives usually are mounted at the top of the blind, and are operatively connected or coupled to the shaft about which the blind lift cords are wound. As described above, as the blind is lowered, the slat weight supported by the lift cords decreases and the compression of the pleats decreases.
However, in the case of the constant torque flat spring drive, as the blind is lowered (or raised) the torque force of the spring remains relatively constant as the supported slat weight or compression force of the lowering blind decreases, with the result that the spring torque may overcome the decreasing supported weight or the decreasing compression force, and raise the blind in fast, uncontrolled fashion. Also, it may be difficult to keep the blind at a selected position. Furthermore, if the blind is heavy, and requires a strong spring to maintain the blind open, the blind may be particularly susceptible to instability and uncontrolled raising operation when partially or fully extended (closed).
In the case of the coil spring drive, as the blind is lowered, the spring is wound and the energy stored in the coil spring increases, with the result that the increasing torque or force of the spring may then overcome the decreasing supported weight or the decreasing compression force and raise the blind in fast, uncontrolled fashion. Also, and as stated above regarding flat spring-assisted blinds, it may be difficult to keep coil spring-assisted blinds at a selected position and, if the blind is heavy and requires a strong spring to maintain the blind open, the blind may be particularly susceptible to instability and uncontrolled raising operation when partially or fully extended (closed). Conversely, when the coil spring-connected blind is at or near the upper limit of its travel (i.e., is open), the slat weight supported by the lift cords and the pleat compression are at or near maximum, while the coil spring torque is at or near minimum.
Frequently, prior art coil spring drives use latching mechanisms in an attempt to hold the blind or cover in position.